Exam 3 Notes: Set Two
Exam 3 Notes: Set Two Bio 1144
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This 3 page Class Notes was uploaded by Murry on Wednesday March 2, 2016. The Class Notes belongs to Bio 1144 at Mississippi State University taught by Thomas Holder in Spring 2015. Since its upload, it has received 31 views. For similar materials see Biology II in Biology at Mississippi State University.
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Date Created: 03/02/16
Exam 3 Notes: Set 2 Digestive System • Animals are heterotrophic – ingest feeders • Animals needs food for survival, maintenance, growth, & reproduction • The most amount of food energy is needed for reproduction • Gut Tracts: 2 Types 1. Blind Gut § No cavity between gut and body wall § One opening § Least advanced § Ex: jellyfish 2. Tube-Within-A-Tube Arrangement § Advanced form § Flow through digestive tube § Fluid-filled body cavity (coelom) between the gut and body wall § Separate openings (one at each end) § Allows animal to be larger as well as eat larger amounts of food • Hydrolases – digestive enzymes that require water to help speed up chemical reactions o Carbohydrases – break down carbohydrates (sugars) o Proteases – break down proteins o Lipases – break down lipids o Nucleases – break down nucleic acids • Basic Functions of Digestive System o Digestion – breakdown of large molecules into smaller forms; combo of chemical and mechanical means; requires water and enzymes o Absorption – the uptake of digested food by cells lining the gut tract o Transport – moving food through the gut tract o Elimination – formation and excretion of fecal matter; removal of undigested and unabsorbed materials • Alimentary Canal – the digestive tract/tube; has a distinct mouth at one end and an anus at the other end; lined with simple epithelium and smooth muscle o Region of Reception: § Buccal Cavity - the mouth and accessory structures • Both chemical and mechanical digestion occur within the buccal cavity • Jaws, teeth, & tongue move food around and break it into smaller pieces • Salivary glands – saliva (spit) glands that contain water and enzymes called amylase that break down sugars • Pharynx – the back of the mouth cavity; the point that the digestive system and respiratory system cross paths o Region of Conduction – conducting food away from the mouth cavity § Esophagus – tube leading from the mouth cavity to the stomach; lined with simple epithelium and outside of that smooth muscle § Smooth muscle responsible for moving food through entire Alimentary Canal because gravity cannot push food down • Peristalsis – rhythmic, wavelike contractions pushing food through o Region of Storage and Digestion: § Stomach – the storage organ that holds food long enough for it to be more effectively broken down; found mostly in vertebrates • A stretchable sac • Rugae – inner lining of stomach (simple epithelium) that create folds when stomach is empty • The wall of the stomach is made of 3 layers of smooth muscle with cells running in different directions • Churning movements of stomach mixes food around so everything is exposed to enzymes • Enzymes secreted in stomach for chemical digestion o Protein breakdown begins • Pits and glands associated with inner lining; necessary for secretion o Mucous cells – secrete mucous for moisture; water needed for enzymes to break down food o Chief cells – secrete pepsinogen o Parietal cells – secrete hydrochloric acid o Pepsinogen + HCl à pepsin o Pepsin – an enzyme that provides for the breakdown of proteins • Has minimal amount of absorption; can only absorb things that are lipid soluble (ex: aspirin, alcohol) o Region of Terminal Digestion and Absorption § If it hasn’t been absorbed by this point, it becomes waste § Small Intestine – at the end of stomach; responsible for majority of food absorption (about 99%) • Digestion of lipids and nucleic acids started and completed here • Digestion of carbs and proteins continued and completed here • About 8x the height of the organism (if you are 5ft tall, you have about 40ft of small intestine) • Has a small diameter • The longer the small intestine, the more absorption it does • 3 Regions of Small Intestine: o Duodenum – beginning; many secretions in this region o Jejunum – middle o Ileum – end • How Does Most of Absorption Occur Here? o Lined with simple epithelium o Has smooth muscle and blood vessels to help move and transport o Surface lining modifications to increase absorption: § Plicae circulares – folds of the inner lining; increases surface areas 2-3x § Villi – finger-like projections into cavity; increases surface area 10x § Microvilli – folding of plasma membrane of cells lining each villus; increases surface area 20x o Region of Water Absorption and Concentration of Solids § Large Intestine – absorbs water and forms fecal matter • About 1.5 meters (much shorter than small intestine) • Single layer of epithelial tissue for water uptake • About 1400ml/nearly 1.5L is absorbed every day • Compacts solids to eliminate waste • Some water lost in order to get ride of waste, but most is absorbed; 75% of waste is water • Waste Composition: o 75% water o 5% inorganic substances o 5% fat o 7% undigested protein, bile, and dead cells o 8% fiber/cellulose/roughage § Anus – the opening to the outside of the body o Cloaca – some vertebrates (all birds & egg laying mammals) have this instead of an anus; a chamber receiving the contents of urinary, digestive, and reproductive tract • Other Organs Associated with Digestive System (but not part of Alimentary Canal) o Pancreas – small gland that has a duct leading to the duodenum; secretes juices that helps with digestion o Liver – produces bile which is absolutely necessary for breakdown of large fat molecules o Gall Bladder – stores the bile and releases it into the duodenum • Carbohydrates à polysaccharides à mono & disaccharides • Proteins à polypeptides à amino acids • Fats à glycerol and fatty acids • Nucleic Acids à nucleotides
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